May 15 2007
A super stable fiber-optic network that can be tuned across a range of visible and near-infrared frequencies while synchronizing the oscillations of light waves from different sources has been demonstrated at the国家标准技术研究所（NIST）. The flexible network design can simplify accurate comparisons of the latest atomic clocks operating at different frequencies and in different locations. The research also may have applications in remote sensing and secure communications.
在“自然光子学”的可能发行中描述的原型NIST网络展示了从两个“频率梳子”，高级实验室工具中的第一个远程同步，用于精确测量光频率。这两个梳具有精细的“牙齿”，标记了不同但重叠的带中精确的频率。如果合并了相同频率处的光波，则它们可以完全重叠或“不相同”（也就是说，它们的振荡频率是相同的，但在不同的时间开始）。不同频率的光波永远不会完全重叠，但是在重复实验中，可以付出巨大的努力以相同的模式重叠。NIST网络旨在完全做到这一点，从而减少了由不匹配而导致的“噪声”的通道。激光的稳定性和同步波的低“抖动”意味着原始信号特征始终保留。
该网络还以来自Erbium纤维激光器产生的频率梳状态展示了记录性能，Erbium纤维激光是由NIST开发的钛sapphire晶体产生的原始频率梳子的替代品。科学家们最近降低了基于纤维的梳子的噪声足以提高其稳定性30倍，从而达到了与最先进的Ti：Sapphire频率梳子相当的性能，用作新的NIST网络中的第二个梳子。基于纤维的频率梳子有可能变得更紧凑，更便宜。他们还测量了电信中使用的较低的近红外光频率。
The prototype network spans three-quarters of a kilometer and connects three different laboratories on the NIST Boulder, Colo., campus. The designers say it could be extended to 50 km or more without any loss in performance. To showcase the capability of the two frequency combs (which operate on different principles) to precisely compare vastly disparate optical frequencies across great distances, both combs are stabilized by the same source of 1126 nm laser light, so that each tooth of each comb is locked to a single frequency. In addition, laser light at 1535 nm laser, stabilized by one comb, is compared to 1535 nm light generated from the second comb, and the stability of the beat frequency (representing the difference between them) is analyzed to evaluate network performance.
http://www.nist.gov
Posetd 2007年5月15日